Camera shutters are mainly categorized into lens shutters and focal plane shutters. The lens shutter is generally mounted near the lens, and the focal plane shutter is generally mounted near the focal plane.
The focal plane shutter is also generally categorized into a horizontal shutter and a vertical shutter depending on the traveling direction of the front and rear curtains. Among these, the vertical shutter is more advantageous in terms of performance and thus has been in wider use.
In a photogaphy apparatus employing focal plane shutter, an image of an object is exposed on a photosensitive surface through a lens as the two curtains, i.e., front and rear curtains, travel. To be specific, as the front curtain travels, the photosensitive surface of the photography apparatus is exposed, and after a predetermined time interval, the rear curtain travels and thus the photography process is finished.
Recently, in order to address problems associated with the mechanical shutter, for example, shock on the front curtain or release time lag generated due to a need for a temporal interval for the charging of the front curtain, many technologies have been introduced to process the front curtain of the focal plane shutter electronically.
One example of these technologies utilizes a reset signal, which is used to initiate the exposure of the respective pixels in an image sensor such as a charge-coupled device (CCD) or CMOS image sensor (CIS) in sequence in the unit of pixel lines and thus replace the function of the front curtain.
A photography apparatus using an electronic shutter generally includes an auto focus (AF) system and an auto exposure (AE) system. The AF system adjusts a focal point of the photographed object automatically, by analyzing differences with respect to an image acquired through the image sensor. The AE system determines the brightness of the photographed object to automatically determine the exposure, in which the opening degree of the aperture and the speed of the shutter are controlled in consideration of the appropriate amount of exposure of the photographed object to set the appropriate exposure automatically.
However, despite the continuous efforts to improve the ‘dynamic range’ (range of highlight and shadow acceptable by the apparatus), even the photography apparatus employing the AE system suffers disadvantages such as distortion of the scene being photographed or degradation of resolution.